1. Field of the invention
The invention relates to a test coupler for supplying a device under test with a test signal, especially within an ultra-broadband frequency range.
2. Related Technology
Electronic test equipment for microwave technology must generally be designed ultra-broadband in order to cover all possible customer applications. The lower frequency limit is then, for example, about 10 MHz with an upper frequency limit of about 60 GHz. The generation and processing of such a frequency range is split internally into several meaningful sub-ranges, which are, however, ultimately combined with one another at the front panel connector of a test equipment. A combination of this kind can be achieved in many different ways. In this context, the use of couplers has proved to be the best solution.
For example, U.S. Pat. No. 5,055,807 B1 discloses a switching between signals of different frequency ranges by means of a coupler and a switch. However, the disadvantage here is the unfavorable electrical properties of the switch, especially its high insertion loss. The high manufacturing costs and the poor long-term stability of a device of this kind are also disadvantageous.
A directional coupler using strip conductor technology, which is, however, not suitable as a test coupler for use with different sub-signals, is known from DE 10 2006 038 029 A1.